Mutagen sensitive strains of Drosophila with different defects in the DNA repair pathway will be used in an attempt to understand the mechanisms of how hyperthermia sensitizes radiation induced genetic aberrations. The increase in loss of chromosomes by hyperthermia and radiation will be determined in mus 101D1, mus 101D2, mus 104D1, mus 105D1, mus 109D1, mei-9a, mei-41A1, and in the double mutants mei-9a-mei41A1. Investigation will be conducted in mutagen sensitive strains located in the third chromosome.